[Beowulf] RE: programming multicore clusters

Joseph Han jhh3851 at yahoo.com
Thu Jun 14 17:04:59 EDT 2007


> Joseph Mack writes:
> 
>  > I expect everyone here knows all this. How is everyone going 
>  > to program the quadcore machines?
> 
> We used OpenMP on the node and MPI between the nodes. It's ugly and
> horrendous to look at or comprehend. The only saving grace is that our
> source code is serial plus custom directives and we have tools to
> generate OpenMP or calls to a MPI based library or both. So we put all
> the difficult stuff in the directives. We don't have any SMP nodes
> anymore so it will take some time to resurrect that ability.
> 
> Using straight MPI is the lowest common denominator and simplest, but
> doesn't use the machine very efficiently. I think it'll only get worse
> with more cores.
> 
> I'd be interested in your experience and what you find out.
> 
> Matt
> 
> 

I don't know the answer to this, but what about MPI implementations which
enable local host optimization automatically?  For example, MPICH, Intel MPI,
and HP-MPI among others all do so if asked.  

Is running a program using OpenMP on a SMP/multi-core box more efficient that
an MPI code with an implementation using localhost optimization?

Joseph

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